1. Field of the Invention
The present invention generally relates to the detection of hydrocarbons in food. More particularly the invention relates to the detection of polyaromatic hydrocarbons in food and environmental samples.
2. Description of the Relevant Art
Oil spills are a source of ecological devastation which poses major threats to the environment and human health. Spilled petroleum can rapidly spread through the sea to contaminate large marine areas. This is especially true for larger oil spills produced by offshore drilling or transportation. Once released into the marine environment, the hydrophobic and persistent characteristics of petroleum create a lingering threat to aquatic life and seafood over vast areas. The persistent, bioaccumulative nature of petroleum causes the extended presence of petroleum constituents in aquatic organisms (including seafood) long after the oil has dissipated from the sea water. Spilled petroleum constituents accumulate in sediments as well as are directly ingested and absorbed by many species of marine life, especially shellfish, where they accumulate over time. Many species of seafood, such as mollusks and crustaceans, do not efficiently metabolize petroleum components which accumulate in their tissues. Consequently, recovery of seafood stocks from large-scale oil spills to baseline hydrocarbon levels can take years.
Petroleum is comprised of a number of components which pose human health concerns, such as alkanes, monoaromatic hydrocarbons, and polycyclic aromatic hydrocarbons (PAHs). PAHs. Exemplary polyaromatic hydrocarbons are depicted in FIG. 1. PAHs are especially troublesome contaminants to deal with after an oil spill, compared to other petroleum components because: i) PAHs have relatively high molecular weights and boiling points so, unlike most alkanes and monoaromatic compounds in petroleum, they are not “weathered” out of the marine environment by atmospheric contact (causing them to remain in the environment over time); ii) they are slowly metabolized in animals; and iii) PAHs can be very toxic and carcinogenic. Toxicology studies indicate that, when ingested, PAHS (such as benzo(a)pyrene and naphthalene) can cause adverse health effects in humans such as cancer, liver damage, birth defects, and testicular toxicity. Some PAH compounds, such as benzo(a)pyrene, are converted to an epoxide form in the liver which can react with DNA to form covalent adducts. These adducts can cause genetic mutations in vivo, especially in the liver. For these reasons petroleum-adulterated seafood cannot be sold in the U.S. Additionally, seafood cannot be harvested from areas affected by oil spills. For example, large fishery areas of the Gulf of Mexico were closed by NOAA because of the Deepwater Horizon/BP oil spill (FDA letter; Jun. 14, 2010). There is now an especially strong need to monitor petroleum constituent levels in seafood in affected areas.
After an oil spill, it is critical to perform quality, high capacity petroleum tests for seafood samples for two reasons: Testing ensures that adulterated seafood does not reach consumers. Additionally, testing provides analysts with valuable information to determine when affected areas have to be closed and, eventually, reopened when samples have returned to baseline levels of petroleum constituents. Currently PAH contamination in seafood is measured using three approved methods: gas chromatography mass spectrometry (GCMS), high performance liquid chromatography (HPLC), and sensory testing (organoleptic “taint” test).
While GCMS is a powerful analytical method, it requires expensive instrumentation, highly-skilled operators, extensive sample prep and it takes considerable time to perform (samples are tested one at a time). While HPLC methods require less sample prep than GCMS, they also require expensive instruments and highly skilled operators. Both GC/MS and HPLC methods require use of toxic organic solvents. GCMS and HPLC methods have limited throughput capacity. In practice, human sensory (organoleptic) testing is now used as an initial primary screen for seafood petroleum adulteration. However, organoleptic methods have their own disadvantages because: i) they are somewhat subjective; ii) they do not provide quantitative data; and iii) they are less accurate and sensitive than GCMS and HPLC, especially for the detection of larger, more carcinogenic PAH compounds. For example, recent comparisons by NOAA of the GCMS and sensory methods using seafood samples from environmental spills indicates that, while sensory testing sometimes agrees well with GCMS results, in a number of cases, samples of whiting, North Cape “finfish”, clams, oyster and mussel containing potentially dangerous levels of PAH compounds (1-24 ppm) did not exhibit any discernible taint. Organoleptic testing also requires skilled, seven member teams in an environmentally-controlled environment. These issues have caused some scientists and seafood producers to question the accuracy and effectiveness of sensory testing.
Immunological methods use antibodies which lack sufficient specificity and robustness for routine, reliable detection of PAH compounds in seafood samples. To increase the accuracy and efficiency of testing, it would be highly desirable to develop new high-throughput, high quality tests for petroleum components in food and environmental samples.